474 Mr. Smith on the structure of 
parietes of the cavity which contains the pulp ; this cavity 
however is never obliterated, but exists in all the teeth of 
serpents, even when they have arrived at their full growth. 
In the fangs, when completely formed, the edges of the 
slit, or suture, are frequently soldered together ; when they 
are angular, so large a surface comes in contact, that they 
appear to be united by bony matter ; in the cobra de capello, 
where they are rounded, though in very close contact, they 
do not cohere. In the viper, the slit seems filled up by the 
enamel, which being nearly transparent, a bristle in the 
poison tube may be seen through it, and causes an appearance 
as if the slit was open. 
In the first case, therefore, there is no channel observable 
on the exterior of the tooth ; the line of junction, however, of 
the edges of the slit is very distinctly marked : in the cobra 
de capello there is an external furrow from the foramen of 
the base to that of the apex, owing to the edges of the slit 
being rounded ; the same is the case in those species of hydrus 
that I have examined. 
I should observe, that the poison tube is not coated with 
enamel ; for the membrane or capsule in which the tooth is 
formed, and from the inner surface of which it is well known 
that the enamel is deposited, does not pass between the edges 
of the slit into the poison tube ; as, however, it passes over 
the slit, it will cover it with enamel, and in some cases, by that 
means alone, the edges become soldered together. 
As some excuse for the errors which may be found in this 
paper, I must observe, that many of my observations have 
been confined to small teeth of a species of hydrus, which I 
Was therefore obliged to dissect under the microscope. 
